The cake is a really nice, simple cardamom cake I originally learned about here, link below. No baking powder, beaten eggs are the leavening.
I made it once before with all-purpose flour, completely forgot to put any sugar in the batter, beat it with a hand mixer for 5 minutes even though I was afraid it hadn't achieved 3 times the original volume yet, baked it at 350 in a 9" spring-form pan, and it came out as a nice little single-layer cake. (The baked sugar topping compensated for lack in the batter.)
Here at home I made it with Swansdown cake flour (no leavening added), an additional 2 tbsp per cup of flour, remembered the sugar, mixed it in a stand mixer on #3/medium speed, and it got thick enough to toss little flips from the beaters long before 5 minutes was up, folded the flour and butter in like I was bathing a sleeping newborn, then baked it at 350 in an 8+" spring-form pan, which it filled a bit more than 3/4--okay because the beating is the only leavening and so it's not going to rise much more, right?
Wrong! It puffed up big time, batter running down the sides, etc. In the end, after about 65-70 minutes it had a very thick, hard crust on top but a toothpick came out clean. Not exactly. Below the thick crust was mostly air space (so clean toothpick!) with the rest of the batter still liquidy over a sugar-nut bottom crust. (I pulled the top "cookie" off and finished baking the batter, so it's ediblish with good, sweet flavor, but what a disappointing mess.)
Please tell me, where'd I go wrong? We really like this cake. Btw, I'll probably halve the sugar permanently. Thanks.